Energy efficient insulated glass unit

ABSTRACT

An insulated glass unit (IGU) comprises impact resistant safety films on the inner surfaces of the glass panes, providing an impact resistant, energy-saving IGU for use in windows and doors. A layer of the safety film providing energy savings may be trimmed from the edges of a glass pane; witch may be sealed within the interior of the IGU, preventing corrosion while providing no loss in impact resistance. A scratch-resistant, chemical vapor deposited coating may be added to an interior glass surface (i.e. facing the building interior) in order to prevent heat loss from the building. An IGU may have an Energy Star rating for both summer and winter use.

RELATED APPLICATION

This present application is a continuation of application Ser. No.10/975,512, filed Oct. 28, 2004, now Allowed and application Ser. No.10/793,958, filed Mar. 5, 2004, now Allowed.

FIELD OF THE INVENTION

The field relates to insulated glass units (IGUs) having a plurality ofglass panes for use in energy efficient windows.

BACKGROUND

Insulated glass windows or door units have been known for many years toreduce the heat transfer between the interior house and the environment.To further improve the insulating properties, the art taught makingsolar control coated and low emissivity (low-E) coated glass or film.Solar control is a term describing the property of regulating the amountof solar heat energy, which is allowed to pass through a glass articleinto an enclosed space such as a building or an automobile interior. Lowemissivity is a term describing the property of an article's surfacewherein the absorption and emission of mid-range infrared radiationsuppressed, making the surface a mid-range infrared reflector andthereby reducing heat flux through the article by attenuating theradiant component of heat transfer to and from the low emissivitysurface. By suppressing solar heat gain, building and automobileinteriors are kept cooler, allowing a reduction in air conditioningrequirements and costs. Efficient low emissivity coatings may improvecomfort during both summer and winter by increasing the thermalinsulating performance of a window, but available glass systems usuallyhave better energy efficiency in retaining heat or blocking sunlight andseldom both due well.

Two typical coating methods to make solar control and low-E coatings are“in-line” and “off-line” coatings. The in-line method uses a chemicaldeposition method involving doping with different chemicals to make aninfrared absorbing layer and low-E layer as described in U.S. Pat. Nos.5,750,265, 5,897,957 and 6,218,018. The off-line method uses sputteringdeposition to make both coatings.

Impact resistant glass is described in detail in the Florida BuildingCode. Basically, it specifies a testing protocol for a window glass towithstand up to nine pounds of force from a 2×4 board shot at the glassup to 50 feet/second. Withstanding both shots with one in the center andone in the corner without penetration is considered as a pass.

U.S. Pat. Nos. 4,799,745 and 5,071,206 describe a multilayeredpolyethyleneterephthalate (PET) window film construction, which givesboth solar control and low-E properties. The coating contains silvermetal layers and indium-tin oxide layers in an alternate construction.The film has a high visible light transmission, above 70%, and a lowvisible light reflection, about 8%. The total solar heat rejection isabout 56%. The color of the coating is light green. It has a very goodsolar control and low-E performances. However, corrosion is a majorconcern. To make an IGU, the window pane needs edge deletion and fillingwith inert gas in the IGU to prevent the coating from corroding. Themulti-layered coating has to be exposed within the IGU to achieve bothlow-E and solar control functions. As a result, the manufacturingprocess for an IGU is expensive and difficult.

U.S. Pat. Nos. 5,332,888 and 6,558,800 disclose a multilayeredsputtering window glass construction (off-line method) which alsoachieves both solar control and low-E properties. The descriptioncontains a silver metal layer sandwiched by zinc oxide layers or asilver metal layer sandwiched by nickel chrome and silica nitritelayers. Similar to sputtered PET film, they also face corrosion,chemical resistant and scratch resistant concerns, which makemanufacturing difficult and expensive.

U.S. Pat. No. 6,546,692 assigned to Film Technologies International,Inc., discloses a method of laminating a safety film on the insidesurfaces in an IGU to build an impact resistant window. The safetyfeature is very important for IGU's to withstand hurricane, earthquake,and terrorism. However, the low-E property is destroyed or significantlyreduced once a safety film is laminated over any low-E coating surface.

Besides solar control, low-E, and impact resistance, other desirableproperties include an economic and repeatable manufacturing process,durability, maintenance, light transmission, visibility, color, clarityand reflection.

To meet the Government (Department of Energy) Energy Star QualificationCriteria for Windows, Doors and Skylights and Florida Building Code forimpact resistant windows, a new IGU is required for the window/doorindustry.

It is known that energy is controlled at a window by the reflection,transmission and absorption of solar radiation by the glazing type andemissivity of the glazing. An Insulated Glass Unit (IGU), which has aplurality of glass panes spaced apart and joined in a unit, contributesto the heat gain or loss of the window by three mechanisms: conductionof heat, convection whereby air currents within the IGU act as thetransfer agent for heat, and radiation or reradiation of the heatabsorbed. When solar radiation strikes an IGU energy is absorbed andeither conducted or reradiated, The ability to reradiate ischaracterized by a surfaces emissivity

When a spectrally selective, vacuum deposited, metal or metallic coatingis incorporated into the surface within an IGU, it assists with energyrelease by absorbing the IR portion of the solar spectrum andreradiating the absorbed energy to the surrounding atmosphere in thedirection of the surface of the coating and the atmosphere interface. Ifthe spectrally selective coating is encapsulated within a film systemand the coating itself is not exposed to the environment, it has beendiscovered that the majority of the ability to reradiate energy is lostas conduction becomes the major pathway for the absorbed energy. Thus,it is important for a spectrally selective coating to be exposed to anatmosphere or void if surface emissivity is used for reradiation of theabsorbed energy. Standard laminated glass where two pieces of glass areadhered together by a plastic and have no void or atmosphere separatingthe glass panes do not incorporate spectrally selective, vacuumdeposited, metal or metallic coatings, because these coatings would notbe effective in emitting absorbed energy back to the outside of thelaminated window unit.

Also it is known that the reactivity of spectrally selective coatingsconsisting of multi-layers of vacuum deposited or sputter-depositedmetals or metallic compounds can corrode depending on the chemicalcomposition when exposed to moisture, light. or other chemicals. Whenthis happens the corrosion products are aesthetically displeasing andthe solar radiation controlling performance of the coatings is lost.

SUMMARY OF THE INVENTION

The ability to incorporate a spectrally selective, vacuum deposited,metal or metallic coating

within an IGU utilizing a film composite having an emitting coating onthe inner surface or surfaces of the IGU provides enhanced absorbed heatdissipation capability as it takes advantage of the filtering out of IRlight, absorbs most of the UV portion of the spectrum, allows forneutral colored visible light to be transmitted, and takes advantage ofthe emissivity of the coating to reradiate absorbed light. This providesfor a better insulation value for the IGU portion of the window andenhanced safety performance because of the film laminate adhered to theinner surface of the glass.

Spectrally selective coatings are protected immediately aftermanufacturing a multi-layered film composite by providing temporaryprotective film which can be removed without harming the spectrallyselective metallic film. This allows handling, shipping and processingwithout damaging the spectrally selective coating prior to completion ofan IGU incorporating the film. The protective film is removed justbefore IGU manufacture which then incorporates these spectrallyselective coatings within the cavity of an IGU. The cavity exposes thefilms, to a benign environment, substantially free of moisture. Thesemeasures ensure the integrity of the spectrally selective coating andthe long term performance of the IGU as a superior insulator. Spectrallyselective, vacuum deposited or sputter-deposited, metal or metalliccoatings on a surface of a multi-ply plastic film composite in an IGUprovides both impact resistance and energy efficiency without corrodingthe metallic coating.

For example, a glass substrates adapted for insertion into frame unit ofan IGU by laminating film composite comprising a metallized coating onan outer layer of a thin, multi-film base to the glass pane, Aprotective film is temporarily applied over the metallized layer untilthe film is adhesively bonded to the glass pane, which is then sealedwithin the interior space of the IGU. The protective film is removed andan outer edge strip of the outer layer of the multi-film layer may bestripped away. The glass pane surfaces may be mounted in a frame with ametallized layer facing inwardly toward the opposite glass pane. Aspacer keeps the glass panes apart and sealant is placed in the cavityformed by the space between the glass panes and the spacer to form asealed IGU.

An advantage of the IGU is improved impact resistance combined with anenergy efficiency that earns the Department of Energy Star Qualificationcriteria. Such an IGU may meet or exceed requirements of Florida andMiami Dade County for large missile impact, also. The process providesfor a comparatively low cost and corrosion/discoloration free low energywindow coating on an IGU.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is best understood by those having ordinary skill in theart by reference to the following detailed description when consideredin conjunction with the accompanying drawings:

FIG. 1 is an exploded cross sectional view of a film composite of thisinvention containing a metallized layer.

FIG. 2 is an exploded cross sectional view of the film composite of FIG.1 with a protective film over the metallized layer.

FIG. 3 is a cross sectional view of the film composite of FIG. 2 aboutto be bonded to a glass pane.

FIG. 4 is a cross sectional view of the outer film metallized layer edgestripped away.

FIG. 5 is a cross sectional view of two glass panes adapted for mountingin a frame with a spacer in between two film composite metallizedlayers.

FIG. 6 is a cross sectional view of two glass panes adapted for mountingin a frame with a spacer in between a film composite metallized layerand a non-metallized layer.

FIG. 7 is a cross sectional view of the two glass panes of FIG. 5mounted in a frame.

FIG. 8 is a side elevational view of an insulated glass window of thisinvention mounted in a window frame.

FIG. 9 is a transmission spectrum of a glass pane on which is applied asolar control layer and a low-E layer on one surface.

FIG. 10 is a transmission spectrum of a glass pane on which is appliedan alternate antimony based solar control and low-E coating.

FIG. 11 is a transmission spectrum of a glass pane on which is applied alow-E coating.

DETAILED DESCRIPTION

In the example of FIGS. 1 and 2, a film composite 10 is formed bylaminating several layers of polyethyleneterephthalate (PET) filmstogether. PET film layers 12 and 14 are held together by acrylicpressure sensitive adhesive 16 and PET film layer 18 is bonded to PETfilm layer 14 by acrylic pressure sensitive adhesive 20. PET layer 18incorporates a spectrally selective vacuum deposited metallic coating 22and protective coating is applied to the outer side of PET layer 18 toprotect coating 22. In alternative examples, the method applies themetallized coating to the outer layer film 18 either before or after theouter layer of film 18 is adhesively bonded with an adjacent layer ofmulti-layered film composite film.

The individual plies of PET 14 and 16 do not have to be of the samethickness and are held together with the acrylic pressure sensitiveadhesive 20. The different layers of PET film 12 and 14 can equal orvary significantly in thickness depending on desired properties, i.e., 2mils laminated with mils, or 4 mils laminated to 4 mils, or 1 millaminated to mils, etc. It is typical for the spectrally controlling PETfilm 18 to be based on a 1 to 3 mil PET film, but can be thicker. Theresulting film composite 10 is classified as a safety film and is usedto coat a window pane 26 as shown in FIGS. 3 and 4 by attachment withacrylic adhesive 28. This composite film thickness can vary from 4 milsto 30 mils total depending on the end use desired and the choice ofindividual PET film thickness. Other safety film can be used and theindividual ply thickness can vary as can the number of plies used tomanufacture the film composite. These films can be made of polycarbonatepolyester or other like polymeric materials. It is important that duringthe manufacturing of the composite 10 that a protective, temporary,masking film is applied to protect the spectrally selective film 18 fromthe environment and contamination. The laminated film composite islaminated to one surface of the glass pane 26 with adhesive 28.

Just prior to manufacturing the IGU, the protective coating 24 isremoved from the glass/laminated film composite surfaces as seen in FIG.4. With care, and using the edge of the glass 26, a cut 32 through theoutermost layer 18 of the film composite 10 parallel with the edge 30 ofthe glass 26 made on all sides of the glass/film composite laminate.Care is taken to only cut through the outer film 18 and to not disturbthe other plies of PET film. The cut 32 is typically from 3/16″ to “fromthe edge 30 of the glass 26. The thin strip, bordered by the edge 30 ofthe glass, formed from the cut 32 is then removed leaving a pictureframe appearance, FIG. 4, to the glass pane.

A glass pane/laminated film composite 10 a shown in FIG. 6 can besimilarly made using only PET films and not incorporating a spectrallycontrolled film. This too is classified as a safety film and isdescribed in U.S. Pat. No. 6,546,692, incorporated herein by reference.

If desired, for aesthetics or performance, layers of colored film can beused with the film composites 10 and 10 a. The color will influence theoverall transmitted light but will not adversely influence theemissivity of the exposed spectrally selective coating.

Two of the laminated window panes shown in FIG. 5 are faced to eachother with the spectrally selective coatings facing inward and a spacer34 shown in FIGS. 5 and 6 having a top inboard surface 36 and a bottomoutboard surface 38 is placed between the laminated surfaces of the twopanes 26 and 40 and pressed together to form a multiple window panecomposite or IGU shown in FIGS. 5 and 6. A structural silicone or butylor like IGU glazing sealant 42 is backfilled from the outboard surface38 of the spacer 34 to the edge 30 of the laminated window pane windowas seated in a frame 44 as seen in FIG. 7. The IGU is preferablypositioned on a setting block when installed in frame 44. The panes alsocan be used in a door system.

As an al ternate IGU composition, one can laminate to one of the panes40 in the above IGU a glass/film composite 10 a whereby there is nospectrally controlling layer in the film composite When this glass/filmcomposite 10 a is substituted in the pane 40 utilizing a spectrallycontrolling film layer 22 is not a needed. Then there is no need toremove a portion of the film composite as there is no spectrallyselective coating to corrode. The film composite 10 or 10 a can coverthe total pane. The resulting IGU made with using one pane 26 with aspectrally controlling layer and one pane 40 without a spectrallycontrolling layer is shown in FIG. 6.

The spacer 34 employed should have a thickness sufficient so itsoutboard surface 38 extends about ¼″ to ⅝″ from the window pane edge 30and its inboard surface is on the site line” of the window frame of thewindow in which it is placed. The width of the spacer 34 between thelaminated window panes should be about ¼″ to 9/16″ but may be smaller orlarger in order to allow for an overall thickness appropriate for thewindow in which it is being glazed.

Typically, a desiccant agent is incorporated with the spacer system inorder to initially scavenge residual moisture within the IGU cavity andthroughout the service life of the IGU.

Inert gas or mixtures may be used to replace the air within the IGUcavity and these techniques are well known within the industry. Theinert gas or mixtures aid with the insulating performance of the IGU bymitigating the convection pathway for heat transfer, especially whenincorporating a spectrally selective coating on the inside of the IGUcavity to emit absorbed energy.

The dimension by which the framing system overlaps the edge of theglazing infill or IGU should be between ˜ to 1 inch with ⅝″ to ⅞″ beingpreferred.

The minimum glass pane 26 or 40 thickness will vary depending on thearea of use, wind load chart and building codes. About ⅜″ glass issuitable in most areas with a laminated film inner surface thickness of0.0008 to 0.02 inch.

To meet solar control criteria, it would be ideal to coat a solarreflective coating on the exterior surface of a window pane. However,because of environmental aging, chemical reaction, corrosion orscratching caused by cleaning the window, the coating cannot be placedon the exterior surface.

Referring to FIG. 8, a solar control coating 112 is coated on the insidesurface 102 of the first glass pane 114. The coating can be made eitherby sputtering deposition or chemical deposition method. A sputteredcoating, as used in FIG. 9, has silver or other IR reflective metallayers sandwiched by metal oxide layers. This coating reflects moreinfrared rays than it absorbs. The metal composite provides the windowglass with high visible light transmission and low visible lightreflection as well as low-E properties. As a result, it is an ideal heatmirror product. The chemical vapor deposition coating has betterchemical and scratch resistance than the sputtering coated product. Itwill absorb solar energy instead of reflect it. As a result, it builds aheat stress over the glass pane and could cause glass breakage. Anotherdisadvantage is that it has a lower visible light transmission thansputtering coated glass to achieve the similar solar performance. Thetransmission spectra for the preferred solar control coatings are shownin FIG. 9 and FIG. 10. The most preferred solar control coating sold byPittsburg Plate Glass Co. is shown in FIG. 9. A safety film 116 islaminated over the sputtered coating 112 on surface 102 to reinforce theglass and also protect the metal from corrosion and other chemicalreactions during aging. However, once laminated with a safety film, itdestroys or significantly reduces the low-E property.

A safety film 116 is constructed with three layers of clear PET filmlaminated to each other with a pressure sensitive adhesive. The safetyfilm has a thickness of 0.004 to 0.025 inches. The preferred thicknessis 0.008 to 0.018 inches and most preferred is a film thickness of 0.015inches. The adhesive is an acrylic based pressure sensitive type. Thecoat weight of the mounting adhesive, which bonds the safety film to theglass, is between 12-17 Ib/ream. The multi-layered construction isbetter than a single layer PET film because it improves the film'simpact resistance. More layers are better for impact resistance but themulti-layered laminating construction can cause distortion problem.

To meet the low-E requirement, a low-E coated glass film 118 has to beused. The function of the low-E coating 118 is to reflect the mid-rangeinfrared rays and reduce the heat flux through the window glass. Thecoating faces the inside of the room on glass surface 4 as shown in FIG.8. The preferred low-E coating is chemical deposited over the glass. TheE value 03-0.25. The preferred E value is 0.08-0.20. The most preferredE value is 0.17 or lower. The visible light transmission (VLT) of thelow-E glass is 35-90%. The preferred VLT is 60-85%. The most preferredVLT is 80%. The preferred color is neutral or light green. A safety film120 is laminated on the interior surface 103 of glass 122 to reinforcethe interior glass.

The coated window glass 114 or 122 can be any type, such annealed, heatstrengthened or tempered.

EXAMPLE 1

The exterior glass pane 114 uses PPG's SB60 CL-3 sputtered solar controllow-E glass. The dimension is 2.5″×0.5″×⅛″ The glass has a visible lighttransmission (VLT) of 75.9%. The VLT is measured with a Densitometermade by Gretag Macbeth Company. The emissivity reading (E value) is0.05. The data is obtained through an Emissometer manufactured byDevices & Service Company. The color is light yellow green with areading of a*=−2.19, b*=2.04, and L=90.79. Where a* is CIELAB colorspace coordinate defining the red/green axis; b* is CIELAB color spacecoordinate defining the yellow/blue axis; and L is CIELAB color spacecoordinate defining the lightness axis. The color numbers are measuredwith a Spectrogard made by BYK Gardner Company. The transmissionspectrum of the coated glass is measured by Lambda 900 UV/VIS/NIRspectrometer manufactured by Perkin Elmer Company. The spectrum is shownin FIG. 9.

The interior glass pane 122 uses Pilkington North America, Inc., EnergyAdvantage Low-E glass. It is coated on surface through a chemical vapordeposition method. The dimension is the same as the exterior glass pane.The glass has a VLT reading of 79%. The emissivity reading is 0.18. Thecolor light neutral and yellow, a*=−, b*=1, and L=92.50. Thetransmission spectrum of the low-E glass is shown in FIG. 11.

A 15 mil safety film is constructed with three layers of mil clear PETfilm laminated to each other with an acrylic pressure sensitiveadhesive. The coat weight for the laminating adhesive is 11 Ib/ream. Amounting adhesive is used to bond the 15 mil safety film and glasstogether. The mounting adhesive chooses the same adhesive as thelaminating adhesive but has higher coat weight. It is about 16 Ib/ream.A UV absorber added into the adhesive formulation to eliminate UVspectrum from the sun.

An insulating glass unit 110 (IGU) as shown in FIG. 8 is constructed inthe way described as follows. A safety film 116 is laminated to thesolar control coated surface 112 of the exterior glass 114 through alaminator. A clean room environment is required. A second safety film120 is laminated to the noncoated surface of the interior glass 122. Aspacer 114 is positioned to the four edges of the first glass pane 114over the safety film 116. The second glass pane 122 is over lapped tothe first pane with safety film 120 facing the safety film 116 on theinside surface of the first glass 114. The four edges are sealed with anappropriate sealant such as buy tal or silicone sealants. The IGU isfilled with argon gas 126 to improve insulation. The final constructionas shown in FIG. 8 is that solar control coating 112 is on the insidesurface 102 of the exterior glass 114 and the low-E coating 118 is onthe exterior surface 104 of glass 122 facing the inside of a room. Thesafety films 116 and 120 are on the inside surfaces 102 andrespectively, of glass 114 and 122.

Both the exterior solar control glass pane 112 and interior low-E glasspane 122 are laminated with a 15 mil safety film on surfaces 102 and 103respectively, and tested with a Perkin Elmer Lambda 900 uv/vis/nirspectrometer. The emissivity number measured with a digital voltmeter.The data are input into a Window 5.0 program for analyzing windowthermal performance. The software is developed by Lawrence BerkeleyNational Laboratory. The results are listed in Table 1. The U-value isthe amount of conductive heat energy transferred through one square footof a specific glazing system for each temperature difference between theindoor and outdoor air. The lower the U-value, the better insulatingqualities of the glazing system. Solar Heat Gain Coefficient (SHGC) ismeasurement of the percentage of solar energy that is either directlytransmitted or absorbed and then re-radiated into a building. The lowerthe coefficient, the better the window able to reduce solar heat.

A scratch resistance test is conducted with Taber 5130 Abraser. The testfollows the ASTM D 1003 method. After 100 cycle abrasion, the delta hazefor the low-E coating on the Pilkington North America, Inc., EnergyAdvantage low-E glass 34%. The haze is measured with BYK Gardner s HazeGard Plus meter.

EXAMPLE 2

Exterior glass pane 114 uses Pilkington North America, Inc., Solar Eglass. The dimension is 2.5″×5″×⅛″. The glass has a visible lighttransmission of 60.3%. The emissivity reading is 0.20. The color isblue, a*=−218, b*=−258, L=82.40. The glass has a transmission spectrumshown in FIG. 10.

The interior glass 122 uses Pilkington North America, Inc., EnergyAdvantage Low-E glass. Following the same process as set forth forExample 1, an IGU is made and tested. The U-value and SHGC reading arelisted in table 1.

EXAMPLE 3

Exterior glass pane 114 uses PPG's SB60 CL-3 sputtered solar controllow-E glass. The interior glass 122 uses Pilkington s Solar E glass.Following the same process as set forth for Example 1, an IGU is madeand tested. The U-value and SHGC reading are listed in Table 1.

A scratch resistance test is conducted in the same manner as describedin Example 1. After 100 cycles of abrasion testing, the solar controllow-E coating is removed. The glass is clear and has less haze. Thedelta haze is −0.60%.

EXAMPLE 4

Both exterior 114 and interior 122 glass panes are clear glass. Thedimension is the same as described in Example 1.

A 17 mil safety and solar control low-E film constructed in a way that a2 mil sputtering coated solar control low-E film is laminated onto the15 mil safety film with metal surface exposed. The laminating adhesiveis the same acrylic pressure sensitive adhesive as previously described.

An IGU is constructed in the same way as described in Example 1. Theonly difference is that the 17 mil safety and solar control low-E filmis laminated on the inside surface of glass 114, and the 15 mil safetyfilm is laminated on the inside of glass 122. Both exterior 114 andinterior 122 glass panes are clear glass. The U-value and SHGC aredescribed in Table 1.

EXAMPLE 5

Both exterior 114 and interior 122 glass panes use PPG SB60CL-3 solarcontrol low-E glass. An impact resistance unit is built the same way asdescribed in Example 1. The only difference is that the interior glass122 has the sputtering coated solar control and low-E coating. TheU-value and SHGC are measured in Table 1. The energy performance is verygood but corrosion has been found in the lab sample on a surface.

EXAMPLE 6

Exterior glass 114 uses PPG's SB60CL-3 and interior glass uses a clearglass. A safety film is laminated on the inside surfaces of glass 114and 122. The U-value and SHGC are measured and listed in Table 1. Thedata shows that the glass E value is significantly weakened.

EXAMPLE 7 Weathering Test

A safety film is laminated over PPG's SB60CL-3 coating. The glass paneis tested in a QUV chamber for accelerated weathering. The glass sidefaces the UV lamp. The testing follows ASTM G154 methods. After 5,500hours of exposure no corrosion or chemical reaction between the adhesiveand sputtered metal is found. The glass VLT and E-value has not changed.However, the corrosion was found in the uncovered area of the low-Eglass. The mounting adhesive is found slightly yellow after UV exposure.

Corrosion Test

Both Energy Advantage Low-E and Solar E glass panes are placed in abucket filled with a little water. The bucket placed in a 135 F hot roomfor 14 days. No corrosion is found. Both the glasses have very goodcorrosion and chemical resistance. They are made through a chemicalvapor deposition process.

TABLE 1 IGU energy performance data in the center of the glass: TotalVLT No. IG Unit Construction % U-Value SHGC Government Energy StarCriteria ≦0.35 ≦0.40 requirements Example 1 Glass/sb60cl-3SG15 50.1 0.340.32 Mil/Ar/SG15 Mil/glass/EA-low E Example 2 Glass/solar E/SG15 41.70.34 0.40 Mil/Ar/SG15 Mil/glass/EA-low E Example 3 Glass/sb60cl-3/SG1537.2 0.35 0.28 Mil/Ar/SG15 Mil/glass/solar E Example 4 Glass/17 milsolar 58.9 0.26 0.35 E/Ar/SG 15 mil/glass Example 5 SB60cl-3 glass/SG1556.5 0.31 0.30 Mil/Ar/SG15 Mil/sb60cl-3 Glass Example 6 SB60cl-3glass/SG15 62.9 0.46 0.35 Mil/Ar/SG15 Mil/glass

1. An insulated glass unit comprising: a first glass pane having a firstsurface and a second surface opposite of the first surface; a secondglass pane having a third surface and a fourth surface opposite of thethird surface; a first safety film comprised of a plurality of polymerfilms adhesively laminated one to the other is adhesively bonded to thesecond surface of the first glass pane; a second safety film comprisedof a plurality of polymer films adhesively laminated one to the otherand a metallized coating on one surface of the plurality of polymerfilms is adhesively bonded to the third surface of the second glass panesuch that the metallized coating is opposite of the adhesively bondedsurface of the second safety film; a spacer positioned between the firstsafety film on the second surface and the second safety film on thethird surface of the second glass pane, such that the spacer separatesthe first glass pane from the second glass pane; a frame enclosing theperimeter of the first glass pane and the second glass pane such that aspace is defined between the spacer and the frame; and a sealantbackfilled within the space defined by the spacer and the frame suchthat the insulated glass unit is sealed from moisture or damp air. 2.The insulated glass unit of claim 1, wherein the plurality of polymerfilms of the first safety film and the second safety film are ofpolyethylene terephthalate.
 3. The insulated glass unit of claim 2,further comprising an inert gas within a cavity defined by the firstglass pane, the second glass pane, and the spacer.
 4. The insulatedglass unit of claim 1, wherein the first safety film and the secondsafety film have a thickness ranging from 0.004 to 0.0025 inches.
 5. Theinsulated glass unit of claim 1, wherein the metallized coating is apyrolytically applied layer.
 6. The insulated glass unit of claim 1,wherein the metallized coating has an emissivity in a range of0.03-0.30.
 7. The insulated glass unit of claim 6, wherein themetallized coating has a visible light transmission in a range of35-91%.
 8. The insulated glass unit of claim 1, wherein a perimeterportion of the metallized coating is removed before the insulated glassunit is sealed.
 9. The insulated glass unit of claim 1, furthercomprising a low emissivity coating on the fourth surface of the secondglass pane.
 10. The insulated glass unit of claim 9, wherein the lowemissivity coating is scratch resistant.
 11. The insulated glass unit ofclaim 1, further comprising a metallized layer on a surface of the firstsafety film opposite of the surface adhesively bonded to the first glasspane.
 12. The insulated glass unit of claim 11, wherein a perimeterportion of the metallized layer is trimmed before the insulated glassunit is sealed.
 13. The insulated glass unit of claim 1, wherein anultraviolet absorbing material is added to the adhesive used toadhesively bond one or more of the first safety film to the first glasspane on the second safety film to the second glass pane or one of theplurality of polymer films of the first safety film or the second safetyfilm to one of the other of the plurality of polymer films.
 14. Aninsulated glass unit comprising: a first glass pane having a firstsurface and a second surface opposite of the first surface; a sputteredsolar control low emissivity coating on the second surface of the firstglass pane; a second glass pane having a third surface and a fourthsurface opposite of the third surface; a first safety film comprised ofa plurality of polymer films adhesively laminated one to the other isadhesively bonded to the second surface of the first glass pane; asecond safety film comprised of a plurality of polymer films adhesivelylaminated one to the other is adhesively bonded to the third surface ofthe second glass pane; a spacer positioned between the first safety filmon the second surface and the second safety film on the third surface ofthe second glass pane, such that the spacer separates the first glasspane from the second glass pane; a frame enclosing the perimeter of thefirst glass pane and the second glass pane such that a space is definedbetween the spacer and the frame; and a sealant backfilled within thespace defined by the spacer and the frame such that the insulated glassunit is sealed from moisture or damp air.
 15. The insulated glass unitof claim 14, wherein an adhesive comprises an ultraviolet blocking agentand the adhesive is used in one or more of the adhesive laminating ofone or more of the plurality of polymer films or adhesive bonding of thefirst safety film to the first glass pane or the second safety film tothe second glass pane.
 16. The insulated glass unit of claim 14, whereinthe sputtered solar control low emissivity coating is scratch resistant.17. The insulated glass unit of claim 14, wherein the sputtered solarcontrol low emissivity coating has an emissivity in a range of0.03-0.30.
 18. The insulated glass unit of claim 14, wherein thesputtered solar control low emissivity coating has a visible lighttransmission in a range of 35-91%.
 19. The insulated glass unit of claim14, wherein the plurality of polymer films of the first safety film andthe second safety film are of polyethylene terephthalate.
 20. Theinsulated glass unit of claim 14, wherein the first safety film and thesecond safety film have a thickness ranging from 0.004 to 0.0025 inches.